Coordinated Inertial Control Method of Doubly Fed Induction Generators and Battery Energy Storage System for Short-Term Frequency Support

Abstract

The high penetration of wind energy brings chal-lenges to the frequency stability of power systems. The doubly fed induction generator (DFIG) is desired to provide inertia sup-port by releasing kinetic energy (KE). However, it may cause over-deceleration and a secondary frequency drop. The installation of a battery energy storage system (BESS) is an effective way to solve the problem. This paper proposes a coordinated inertial control method of DFIGs and BESS for wind power plant (WPP) to support short-term frequency and enhance the frequency na-dir. The equivalent inertia of the WPP is analyzed to allocate power for each DFIG and BESS. In the proposed method, a state of charge (SOC) distribution factor is first proposed to calculate the active power reference of DFIGs and BESS. Then, the allo-cated power reference of each DFIG can be obtained according to its level of KE. The goal of the proposed control method is to avoid the severe SOC decrease and the over-deceleration of DFIG, thus a stable effect for short-term frequency support can be ensured. Simulations performed in DIgSILENT/PowerFactory show the proposed control method has a good performance in improving the frequency nadir, keeping the levels of SOC and KE.